1. Classification
based on operations performed:
1.Shearing
· Piercing
· Punching
· Perforating
· Blanking
· Cutting off
· Parting off
· Notching
· Slitting
· Lancing
2. Bending
· Angle bending
· Curling
· Forming
· Plunging
3.Drawing
· Cupping
4.Squeezing
· Coining
· Embossing
· Flattening
2. Classification
based on construction:
· Simple
· Follow or progressive
· Combination
· Compound
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Source: Press Operation Classification
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EXPLANATION ACCORDING
TO OPERATIONS:
1. Shearing
operation: The shearing operation between a punch
and a die is illustrated in Fig. As the punch descends upon the workpiece, the
pressure exerted by the punch causes the metal to be deformed plastically in
the die.
· Piercing: The piercing is the
operation of production of hole in a sheet metal by the punch and the die. The
materials punched out to form the hole constitute the waste.
· Punching: The punching
operation is similar to the piercing operation. While punching the formation of
the hole is the desired result. The difference between the punching and the
piercing is that in the case of punching a cylindrical hole is produced,
whereas in the case of piercing the hole produced may be of any other shape.
· Blanking: The blanking is the
operation of cutting of flat sheet to the desired shape. The metal punched out
is the required product and the plate with the hole left on the die goes as
waste.
· Perforating: The perforating is the operation
of production of a number of holes evenly spaced in a regular pattern on a
sheet metal
· Parting: The parting is the
operation of cutting a sheet metal in two parts. Unlike cutting off operation,
some quality of scrap is removed to severe the workpiece in two parts.
·
· Cutting off: The cutting off is
the operation of severing a piece from a sheet of metal or a bar with a cut
along a single line.
·
· Notching: The notching is the
operation of removal of the desired shape from the edge of a plate. The punch
and the die set up are similar to the piercing or punching operation.
· Slitting: The slitting is the
operation of cutting a sheet metal in a straight line along the length.
· Lancing: The lancing is the
operation of cutting a sheet metal through part of its length and then bending
the cut portion.
2. Bending
operation:
The bending operation
is illustrated in Fig. While bending, the metal is stressed in both tension and
compression at the two sides of the neutral axis beyond the elastic limit but
below the ultimate strength of the material.
· Angle bending: The angle bending is
the operation of bending a sheet metal to the sharp angle. The punch and the
die are shaped to the desired angle. The punch and the die are shaped to the
desired angle, taking into consideration the effect of spring back. The angle
bending operation is illustrated in Fig.
· Curling: The curling is the operation of forming
the edges of a component into a roll or a curl by bending the sheet metal in
order to strengthen the edges and to provide smoothness to its surface. The
curling operation is illustrated in Fig.
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Curling
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· Forming: The forming is the operation of bending
a sheet of metal along a curved axis. The metal is confined between the punch
and the die and is stressed in compression and tension beyond the elastic
limit. The shape of the component is governed by the shape of the punch and the
die.
· Plunging: The plunging is the operation of
bending a sheet metal to the desired shape for accommodating a screw or a rod
through the plunged hole. The plate is first pierced at the required position
and then the plunging punch is pressed in the hole.
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Plunging -Press Operations
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3. Drawing
operation:
The drawing is the
operation of production of cup shaped parts from flat sheet metal blanks by
bending and plastic flow of the metal. The operation is also known as cupping.
The drawing operation is illustrated in Fig.
4. Squeezing
operation:
The squeezing
operation is the most severe of all cold press operation. Tremendous amount of
pressure is required to squeeze a metal which is made to flow in a cold state
within the cavity of the die and the punch to attain the desired shape. For
this reason the squeezing operation is performed in a hydraulic press. The
different squeezing operations are described below:
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Embossing and Coining Process
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Coining: The coining is the operation of production of coins, medals or other ornamental parts by squeezing operation.
Embossing: The embossing is the operation of giving impressions of figures, letters or designs on sheet metal parts. The punch, or the die, or both of them may have the engravings which are marked on the sheet metal by squeezing and plastic flow of the metal.
Flattening or planishing: The flattening or planishing is the operation of straightening a sheet metal which is a curved one. The operation is illustrated in Fig. The pin pointed planishing tool is made to descend on the sheet metal to be straightened, and the projections on the tool exert tremendous pressure on the plate to remove all the residual bending stress present in the plate.
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